Recently, an ultra-high vacuum technique has been regarded as important along with remarkable development of a nanotechnology and an ultra-precision measurement technique. For example, a surface of a semiconductor is easily contaminated by gas molecules, and conventionally, there has been a need of maintaining the semiconductor in an ultra-high vacuum state under 10−5 Pa or lower to keep the clean semiconductor surface. In addition, a field emission type charged particle source is used in a charged particle beam device, for example, which uses a finely focused electron beam or an ion source such as a scanning electron microscope in order to improve resolution. At this time, it is necessary to maintain an internal space of the charged particle source in the ultra-high vacuum state in order to stably operate this field emission type charged particle source. Thus, conventionally, an ultra-high vacuum pump such as an ion pump has been used as a device configured for the formation of the ultra-high vacuum state.
In this manner, the ultra-high vacuum environment under 10−5 Pa or lower, particularly, a class of 10−9 Pa to 10−7 Pa provides ultimate cleanness and stability, and thus, is indispensable for nanoscale ultra-precision machining, ultra-precision measurement, and the like. Conventionally, however, it has been considered that an exhaust device such as a bulky ion pump and a cryopump is necessary for creation and maintenance of such ultra-high vacuum environment. In this manner, the exhaust device has a large-scale structure, a chamber housing the device becomes bulky, and as a result, there is a problem that the entire device scale becomes unnecessarily larger and heavier.
Thus, a light, small and highly efficient ion pump having uniaxially symmetric electrode arrangement has been developed (Patent Literature 1) in order to solve the above-described problem and a cylindrical ion pump with a larger exhaust amount has been developed (Patent Literature 2) as an evolved type thereof. In particular, the ion pump described in Patent Literature 2 is the cylindrical ion pump in which a space with little electromagnetic field modulation, configured to store a sample and a charged particle source, is secured at the center thereof, and a pump element (a permanent magnet or the like) is arranged in the form of being stuck to a casing surface of an ultra-high vacuum chamber. Thus, it is revolutionary in terms that it is possible to realize high exhaust performance and space efficiency at the same time.